In a filling process of producing packaged beverages (canned beverages, beverages in PET bottles, bottled beverages), the beverage is typically caused to flow from above into a container disposed vertically in a filling machine (filler) and then the container is joined to a lid member and sealed in a sealing machine (a seaming machine, a capper, and the like). In order to maintain the beverage quality and improve flavor, it is important that the amount of residual oxygen in the sealed container be reduced. The removal of oxygen from the headspace inside the container is especially important. A deoxidation technique such as undercover gas displacement performed immediately prior to sealing has been developed and used to realize such a removal. On the other hand, because packaged beverages are products consumed in large amounts, the rate of the filling process has been increased and, in the case of canned beverages, high-speed lines capable of producing 1000 to 2000 cans per minute have been put to practical use. Following the beverage filling process, foam is generated inside the container. Foam generation behavior and destruction behavior differ depending on the properties of individual beverages and filling conditions, but typically when the production rate is high, a large amount of foam is generated, the available time is insufficient for destroying the foam, and foam remains during sealing.
Foam contains oxygen at the same concentration level as the air, and because the oxygen contained in the foam cannot be removed by gas displacement in the headspace, the foam makes it difficult to decrease the amount of oxygen in the headspace. In particular, at present advanced level of deoxidation technology based on gas displacement, the remaining oxygen is mainly due to foam. Admixing a defoaming agent to a beverage preparation is presently generally employed to inhibit foam, but because the defoaming agent affects the beverage taste, a technology capable of defoaming after filling and before sealing is needed.
A method for defoaming by light irradiation has been considered as means for resolving this problem, and a large number of methods and devices relating to this technology have been suggested (see, for example, Patent Documents 1 to 4). Methods for laser beam irradiation have also been suggested. For example, a method for defoaming with laser radiation has been suggested by which intermolecular bonds forming a foam film and organic molecules or water molecules contained in the film are caused to oscillate and excited by irradiating foam with a laser beam, the intermolecular bonds are broken and foam is destroyed (see Patent Document 4).
Methods and devices for defoaming by irradiation with ultrasonic waves have also been suggested (see Patent Documents 5-9). Further, in addition to methods and devices using light and sound, those using heating, microwaves, high frequency, electric discharge, electric wind, electrostatic charges, and vapors have also been suggested.    Patent Document 1: Japanese Utility Model Application Laid-open No. 53-102178.    Patent Document 2: Japanese Utility Model Application Laid-open No. 60-31306.    Patent Document 3: Japanese Patent Application Laid-open No. 63-104620.    Patent Document 4: Japanese Patent Application Laid-open No. 63-252509.    Patent Document 5: Japanese Patent Application Laid-open No. 11-90330.    Patent Document 6: Japanese Patent Application Laid-open No. 7-291395.    Patent Document 7: Japanese Patent Application Laid-open No. 9-328193.    Patent Document 8: Japanese Utility Model Application Laid-open No. 62-90397.    Patent Document 9: Japanese Patent Application Laid-open No. 6-191595.